1. Technical Field
The present invention relates to an angle measuring device and measuring method of an object utilizing an optical system.
2. Description of Related Art
As a related angle measuring method utilizing an optical system, there is, for example, an optical lever system to measure an angle by using the inclination of a laser light. This utilizes the phenomenon that, when a laser light is made incident on a mirror attached to the object, an angle of deviation of reflected light becomes 2θ when the mirror is inclined by θ.
FIG. 14 is a schematic structural view of a related angle measuring device that employs the optical lever system. In FIG. 14, laser light emitted from a light source 501 is reflected by a beam splitter 502 and thereafter transmitted through a quarter wavelength plate 503, formed into parallel light by a collimator lens 504 and applied to an object 505. The reflected light reflected on the object 505 is condensed by the collimator lens 504, transmitted through the quarter wavelength plate 503, transmitted through the beam splitter 502 and formed as an image on a photodetector 506.
With the above construction, the angle of the object 505 is measured according to the image location in the photodetector 506. For example, when an angle formed between the optical axis S of the collimator lens 504 and the object 505 is zero, i.e., if the image location when a flat surface 505a of the object 505 is arranged generally perpendicularly to the optical axis S is previously known, the angle of the object 505 is measured from a mutual relation between the image location and the measurement position.
As such an angle measuring method of the optical lever system, there is a method disclosed in, for example, Japanese patent application publications No. 2001-133232 and No. 2003-083731.